Embodiments relate generally to seismic sensor cables (or simply “sensor cables”) for marine geophysical surveys. More particularly, embodiments relate to a sensor cable that may be reconfigurable to have various combinations of seismic sensors.
Techniques for marine geophysical surveying include seismic surveying, in which geophysical data may be collected from below the Earth's surface. Seismic surveying has applications in mineral and energy exploration and production to help identify locations of hydrocarbon-bearing formations. Seismic surveying typically may be performed using sensor cables, such as “streamers” that may be towed through a body of water or “ocean bottom cables” that may be located on the water bottom. The sensors cables may include a plurality of seismic sensors, such as hydrophones, particle motion sensors, accelerometers, geophones, etc., disposed thereon at spaced apart locations along the length of each cable. In a typical seismic survey, one or more seismic sources may be actuated to generate, for example, seismic energy that travels downwardly through the water and into the subsurface rock. Seismic energy that interacts with interfaces, generally at the interfaces between layers of rock formations, may be reflected toward the surface and detected by the seismic sensors on the sensor cables. The seismic energy may be reflected when there is a difference in acoustic impedance between the layer above the interface and the layer below the interface. The detected energy may be used to infer certain properties of the subsurface rock, such as structure, mineral composition and fluid content, thereby providing information useful in the recovery of hydrocarbons.
Currently, a typical sensor cable may contain a limited quantity of seismic sensors (e.g., hydrophones, particle motion sensors, accelerometers, geophones, etc.) distributed evenly or variably along the length of the streamer. Seismic sensors such as hydrophones may be arranged in various configurations along the sensor cable. FIG. 1 illustrates an example sensor cable 10 that may comprise inline seismic sensors 12 disposed at spaced apart locations along a length of the sensor cable 10. The inline seismic sensors 12 may be arranged in what is generally known as a “group-forming” technique. As illustrated, the inline seismic sensors 12 may be arranged in sampling groups 14 in which the signals recorded by the inline seismic sensors 12 in each group may be combined or summed in various ways.
There may be drawbacks to the conventional group-forming technique. For instance, the sampling of locations assigned to the sampling groups 14 or the sampling of the individual inline seismic sensors 12 may be fixed. The inline seismic sensors 12 in the sampling groups 14 may be spaced at a fixed distance, typically at least about 60 cm. Moreover, the sampling distance is generally limited by the functionality of the hardware that connects the inline seismic sensors 12 in the sampling groups 14.